Effects of calving and submarine melting on steady states and stability of buttressed marine ice sheets

Abstract

Mass loss from ice shelves is a strong control on grounding-line dynamics. Here we investigate how calving and submarine melt parameterizations affect steady-state grounding-line positions and their stability. Our results indicate that different calving laws with the same melt parameterization result in more diverse steady-state ice-sheet configurations than different melt parameterizations with the same calving law. We show that the backstress at the grounding line depends on the integrated ice-shelf mass flux. Consequently, ice shelves are most sensitive to high melt rates in the vicinity of their grounding lines. For the same shelf-averaged melt rates, different melt parameterizations can lead to very different ice-shelf configurations and grounding-line positions. If the melt rate depends on the slope of the ice-shelf draft, then the positive feedback between increased melting and steepening of the slope can lead to singular melt rates at the ice-shelf front, producing an apparent lower limit of the shelf front thickness as the ice thickness vanishes over a small boundary layer. Our results illustrate that the evolution of marine ice sheets is highly dependent on ice-shelf mass loss mechanisms, and that existing parameterizations can lead to a wide range of modelled grounding-line behaviours.

AMOC Stabilization Under the Interaction With Tipping Polar Ice Sheets

“…However, we can expect our qualitative results to hold as long as this interaction remains destabilizing. To better base it on physical grounds, one would have to consider sub‐shelf melting and calving processes, interacting with the ice shelf stability through buttressing (Haseloff & Sergienko, 2018, 2022) and lateral drag (Schoof et al., 2017). Also, a better assessment of the fraction f of the WAIS freshwater flux reaching the southern Atlantic Ocean would be a direct improvement, which involves resolving the dynamics associated to the Antarctic Circumpolar Current and is beyond the scope of this study.…”

Inferring Tide‐Induced Ephemeral Grounding in an Ice‐Shelf‐Stream System: Rutford Ice Stream, West Antarctica

“…Buttressing stress from the ice shelves plays an important role in regulating the ice‐sheet discharge (e.g., Dupont & Alley, 2005; Gudmundsson, 2013; Haseloff & Sergienko, 2018, 2022; Sergienko & Wingham, 2022; Thomas, 1979). Basal shear traction arising from contact between the ice shelf and bathymetric highs is an important factor influencing the buttressing stress and is thought to generate strong short‐timescale tidal variability in ice flows (e.g., Minchew et al., 2017; Padman et al., 2018; Robel et al., 2017).…”

“…Our observations of ephemeral grounding at RIS are at fortnightly timescale, but they highlight the importance of basal shear traction from the observed subshelf bathymetric highs, which can help constrain the long‐term (e.g., 10s of years) change in buttressing stress due to ice‐shelf thinning. Because RIS is strongly laterally confined, the lateral shear is a primary control on the buttressing stresses (e.g., Haseloff & Sergienko, 2018, 2022). However, the basal shear traction from the subshelf bathymetric highs is sensitive to ice‐shelf thinning, which causes immediate shrinkage of the existing zones of ephemeral grounding and further transition into an ungrounded state.…”

Simulating the processes controlling ice-shelf rift paths using damage mechanics

“…Calving and submarine melting are the two major causes of the recent Antarctic losses of ice-shelf mass and buttressing of upstream grounded ice (Greene and others, 2022). Decreased buttressing can affect the discharge of grounded ice into the ocean and ice-sheet contribution to sea-level rise (Haseloff and Sergienko, 2022), and calved icebergs can transport freshwater to lower latitudes to influence ocean circulation and sea-ice growth (e.g. Jongma and others, 2009;Martin and Adcroft, 2010;Merino and others, 2016), as well as the marine biosphere (e.g.…”